hello.. soon here comes a little review on my db10 i built before xmas..but first the box and sub:

used a Hertz ES250, 10" sub.. cheap/big value speaker, really nice sounding sub when used in both sealed and ported design.just had to test it in a DB, just to see what a DB does to a sub, and how the ES250 could do in the box..

it took me 2 evenings, after work to put it together..using 19mm mdf, nd lots of glue but spent the 3rd evening figuring out and build a thingy that makes the tuning of the box much easier without taking the backplate on of all the time.so i built a thingy that let me adjust the baffel from bottom to top easily..pics from and of the build are coming.

just wanna say there was a lack of lows on some of the tracks o tried...in a sealed or ported the same lows is very nice..but in the DB it was just a kind of distorted sound...thats no good so far..

Be sure your crossover is set low enough. It is difficult to distinguish if the distortion is at the frequency you want to hear or at one of the harmonics of that frequency. A low crossover(<80Hz) should filter the harmonics.

You also didn't mention what size sealed box you are comparing the DB to. If the sealed part of the DB can't be adjusted to that size, it sure can't match the sound.

the box is adjustable by a bolt going tru the backplate..the baffle can be adjusted from top to bottom by turning a wheel (on that bolt...)the insert got two gaskets, so its like a piston with piston-rings..get it...?theres a screw that i take out so the pressure in the sealed chamber isnt pushing/pulling the sub, when i`ve adjusted it i put the screw back in and the its sealed off..

i see others trying to tune the box, but it will all change when you seal of the baffel with silicone or something, so i thought having it pretty sealed when tuning would be best.

the car is a hatchback, the box on the right side of the car and the port was facing backwards.

the lowpass was at about 50~55hz 12db, and the sub was getting about 150wrms.maybe it was a lack of power on the lows but the volume wasnt that loud for amp to clip(or fail)..

the sealed box was about the same size as the sealed chamber of the DB.. the DB got louder but there was some low end missing..the same low end on the sealed was louder and no distorted sound.

gonna put some pics up when i get the chance to do it..or when i`m bored..

lol...yes....guess its kinda late.. ;D but don`t find the pics on the pc [smiley=18.gif] so gotta find some memorysticks lying around..

sorry to say that i`ve sold the hertz 10", but the DB is in the office ::) dont have any sub for it , unless i take one of the RE Audio SE10 out of the 750ia.. :P nah..

but if you think of the insert as a piston in an engine and how the pistonrings is in that groove , is the same way the flat self-adhesive rubber-gasket (8mm wide x 3mm thick) is on the insert.

used a bit on the router and made two grooves that was 7mm so the gasket was squeezed into the groove and wouldnt move. i guess its pretty sealed, as i had to stand on the insert and jump on it to get it in..lol.. ps: i guess if you paint and/or sand smooth the innerwall of box the gasket would slide easier..

the adjustment is made by an U / bridge wich is 6"tall and 11.5" wide, going from one corner to the other, on the insert..U/bridge is made of 1" x 1" U-stainlessteel, and it goes over/behind the magnet on most 10" woofers. there`s a 10mm threadrod attached on top, in the middle of the bridge..its a tight fit, but it turns around using washers..tho without moving up and down..

threadrod goes thru the topplate by 6~7", on the topplate there`s a nut welded on a 2" x 2" steelplate, which is screwed on top of mdf.so when turning the threadrod, the nut/plate on the mdf makes it go up~down , and so does the insert....maybe it makes more sence with pics...hehe....but its no hitech science guys...hehe... :P oh..and i used the same gasket on topplate to seal it of..

Sort of like this, except mine is round. Picture shows inner assembly minus outer tube. I just welded a nut on the end of the rod which sits on the outer face of the top plate - adjusts with a spanner.

Interesting you have troubles with lowest of frequencies - I have experienced the same- I also am confident that my design does not leak - but I do get the same fluffy distorted response between the 20 - 25 Hz range. I wasnt sure if it was because the driver's Fs is 24 Hz or - after reading above from you guys, and some kind help from Bart West(Thanks Bart!), I still need to try some inner fill in the sealed section, a lower cutoff (my HT amp sub out cuts off around 100Hz - need to build a crossover module!) before I finally lose the feature I so proudly built and seal it permanantly - the variable tuning.

PC : you`ve created a monster :o tho, mine still got the looks of a DB, its the same thinking.when i think of it, i would guess the lack of lows from my DB was because of the 150wrms it got from the car amp , or the 120wrms it got from the plateamp wasnt enough, and thats why it kinda sounded distorted..sometimes.. dunno...but since i`ve sold the hertz sub and dont have others laying around, i got some peerless 4ohm, 100wrms, 10" in my front speakers, that i could put in the DB and try a 250wrms plate amp on it..

hehe..i got a 12V motor from a el.window that i could mod` to fit my DB , then i could sit in my listening area and adjust tuning by remote....ah..for those lazy days